6．The number of students admitted annually to this school _____ from more than 1,000 in the year 2000 to some 2,000 last year．

A．increases　B．has increased  

C．is increasing　D．increased

7． —I stayed at a hotel while in New York．

—Oh，did you？You _____ with Barbara．

A．could have stayed　B．could stay　

C．would stay　D．must have stayed